We conducted HCD sessions with individuals enrolled in CR at the University of California, San Francisco. During these HCD sessions, we collected qualitative data from participants to develop and iteratively refine the interventions through 4 phases: discover, define, develop, and deliver [19-21]. Our use of HCD is consistent with the broad principles of ISO 9241‐210, which defines HCD as an approach that centers users’ needs and requirements throughout an iterative design process. Specifically, our approach satisfied core HCD principles, including explicit understanding of users, tasks, and context (Session 1); active user involvement throughout the design process; and iterative refinement of interventions based on user-centered feedback (Sessions 2‐3). This structured, user-centered approach helps ensure that interventions are systematically refined, grounded in the lived experiences of patients, and ultimately more likely to be effective in practice. This checklist can be found in Checklist 1.

We recruited a convenience sample of participants who were at least 18 years of age and participating in CR at University of California, San Francisco, an urban academic medical center. Invitations were sent via electronic health record messages. Participants were asked to provide information on gender, race or ethnicity, age, health literacy [22], and perceived social status [23]. Quantitative data were collected and managed using REDCap (Research Electronic Data Capture) electronic data capture tools.

HCD sessions were conducted by trained facilitators over Zoom, with each session lasting 90 to 120 minutes. For each session, we held 2 groups with 2 to 4 participants each. Sessions took place between April 2024 and June 2024.

In Session 1, our aim was to understand participants’ perceptions, thoughts, and behaviors about FIM in the context of the Theory of Planned Behavior [24]. We used a template that integrated themes from the Theory of Planned Behavior to do so. This template can be found in Multimedia Appendix 1. We then took participants through a “User Journey” depicting the steps that a patient would take to participate in a FIM program called Project Open Hand. This instrument can be found in Multimedia Appendix 2. As we went through each step, we asked participants for feedback about what they would like to hear and see at each step of the journey. Based on participant responses, we developed our navigation scripts and text message library. These interventions can be found in Multimedia Appendix 3 and Multimedia Appendix 4, respectively.

Session 2 reviewed the navigation scripts and text message library with participants. Participants provided feedback on each section of the navigation script, as well as the content, length, grammar, and language of the text messages. These materials were revised based on participant feedback.

Session 3 focused on reviewing the refined navigation scripts and text messaging libraries. Additional minor revisions were made based on participant feedback.

Each session was conducted virtually using Zoom and was hosted on 2 different dates to accommodate participant scheduling needs. One primary facilitator (RDO) led each session and interviewed participants using interview guides that were drafted prior to the start of the study. The interview guides can be found in Multimedia Appendix 5. Additional members of the research team (LC and AN) were present to observe and document participant reactions and responses and to prompt further input when appropriate. The investigators did not have prior relationships with any research participants.

This study was approved by the WCG Institutional Review Board (1370693), and procedures were followed in accordance with WCG Institutional Review Board and institutional guidelines. Prior to the start of the first session, participants provided written informed consent. They also provided verbal consent for audio recording prior to the beginning of each session. To protect participant confidentiality and to minimize the possibility of sharing information that could be used for potential reidentification, session transcripts will not be available; however, analysis files may be obtained from the corresponding author upon reasonable request. Participants were compensated US $200 per HCD session for their time and participation.

Twenty-two people were invited to participate in the study: 6 consented and participated, 1 consented but did not participate in any study activities after providing consent, 3 were found to be ineligible, 1 explicitly declined, and 11 did not respond. We enrolled 6 participants, of whom 4 were female and 2 were male, 2 self-identified as Black or African American and 4 as White. All participants spoke English. Participants ranged in decade of age from their 40s to their 80s. Mean perceived social status was 6 (SD 2.6; scale from 1 lowest to 10 highest). Mean health literacy was 2.8 (SD 1; scale from 0 to “Not at all confident filling out medical forms” to 4 “Extremely confident”).

In addition to prespecified themes from the Theory of Planned Behavior, which are (1) attitudes or beliefs about FIM, (2) social influence regarding FIM, and (3) perceived behavioral control, we also identified emergent themes: (4) cost of shopping for healthy foods, (5) culturally appropriate food, (6) local food options, (7) flexibility with FIM programs, (8) ability to give feedback to FIM programs, and (9) personalization. Qualitative themes are described in additional detail below.

Participants generally seemed motivated to eat healthier and agreed that they had all developed different habits unique to their current situations. While there is a consensus that individuals would like to eat healthier, the challenge often lies in having the energy and knowledge to prepare nutritious meals.

Individuals explained habits that they have developed around cooking and eating food based on their current situations and perceived ability to make certain foods.

Furthermore, participants shared that part of the barrier to eating healthy lies in shopping for healthier foods and groceries. These barriers are often out of one’s control. There are multiple factors that individuals must consider when grocery shopping, including cost, current living situation, and shelf life.

Participants expressed a strong desire to eat healthy but acknowledged that this lifestyle can be prohibitively expensive. They also highlighted the stress of budgeting and calculating what they can afford. As a result, many end up eating only what fits their budget, even if it is not healthy.

Cultural appropriateness refers to the idea that there is a match between the foods provided and the cultural food traditions of the patient. Participants cited that the cultural appropriateness of foods is a factor that impacts their eating habits. Therefore, it can be understood that cultural appropriateness is particularly crucial in the context of FIM programs, as it affects the patient’s ability to adhere to the meal plans or cook with the groceries provided.

Many individuals expressed a strong desire to obtain fresh groceries and support local farmers’ markets, as they believe these items are inherently healthier. However, they find farmers’ markets challenging to access due to high prices.

Regarding FIM programs, there was widespread consensus that the program needs to be flexible (ie, with scheduling food services, switching between MTM and MTGs), as patients will have other commitments such as rehabilitation sessions or doctor’s appointments and may desire having meals or groceries delivered depending on their current situation.

Individuals also emphasized that FIM programs should create space for feedback as it empowers patients to be active participants in the program and helps ensure the program remains responsive and adaptable to their needs.

Participants also stressed the need for personalizing the FIM program to each individual. When implementing and explaining the program, they suggested that explanations should be related back to the patient’s unique circumstances. This approach will clarify how the program will impact them personally and will likely increase their motivation and engagement.

These representative quotes, as well as some others, are listed below in Table 1.

Using HCD principles, we worked with people participating in CR to develop 2 interventions to promote enrollment and engagement in a FIM program: navigation and text messaging. Our findings suggest that, overall, participants held positive beliefs about the impact of FIM programs and understood the importance of having a healthy diet. Despite this understanding, there were numerous factors impacting individuals’ eating habits, such as personal beliefs about healthy eating, social influences on the eating habits, cost, and availability of healthy foods. Furthermore, participants emphasized that FIM program design features, such as flexibility, ability to offer feedback, and personalization were important for remaining engaged.

Other barriers, such as financial feasibility and access to healthier foods, were also discussed. Fresh produce is often more expensive and not as readily available locally, and this may impose a financial burden on individuals who come from low-income backgrounds [26]. This leads to unequal access to a healthier diet, further exacerbating the disproportionate burdens and impacts of cardiac illnesses in these populations [27]. Understanding healthy eating within the context of these financial strains is crucial for developing interventions that enhance the effectiveness of FIM programs.

Participants noted that their cardiologist and health care team are key figures in encouraging healthy behaviors. Thus, they emphasized that partnership between these providers and the FIM program is important—not only to monitor the FIM program’s impact on their CV health but also to improve access to these programs, since physicians can often play a central role in initiating referrals. Other studies have similarly found that a strong partnership between health care providers and food pantries, along with a consistent availability of healthy food resources, is vital in ensuring the effectiveness of food prescription programs. For example, one study employed clinic-based interventions in coordination with local food banks and showed measurable improvements in patient outcomes, such as improved blood sugar and blood pressure control [27]. Another qualitative study in Houston revealed that program success relies on clear workflows between clinicians and food pantry staff and the integration of food prescriptions into routine health care [28].

The use of HCD to engage people with lived experiences in the development of an intervention may improve the relevance and acceptability of health behavior interventions. The feedback provided by participants encouraged positive framing, the offering of examples, and practical actions rather than the presentation of information about health consequences. The feedback provided to us demonstrated similar themes consistent with findings from other studies that have used HCD sessions for text messaging. For example, in a study that focused on developing text messages for the prevention of CV disease in people with HIV, participants similarly preferred messages that were short, clear, and actionable. They emphasized the importance of a positive tone over judgmental language and valued advice that was culturally relevant [16]. These patterns, similar to those found in our study, suggest that text message–based interventions are most effective when they deliver brief, actionable, and supportive messages that align with the contextual realities of patients. This approach, if used in future text-based interventions, may enhance engagement, promote behavior change, and ultimately reduce disparities in health outcomes.

Personalizing FIM programs to align with individuals’ unique health goals and nutrition literacy is important for maximizing their effectiveness. Research shows that when nutrition interventions are tailored to an individual’s knowledge level and perceived self-efficacy in making dietary changes, they are more likely to adopt and sustain healthy behaviors [29]. This encourages individuals to make better dietary choices, leading to increased fruit and vegetable intake and a greater ability to manage decisions related to food. As a result, individualized approaches not only allow for greater access to healthier foods but also allow for the development of the skills and confidence required to use them effectively.

Despite having many strengths, our study has limitations that should be acknowledged. Our HCD sessions were conducted with a small number of participants, with each session consisting of only 3 to 4 participants. While a sample of 6 participants is appropriate for our study design, our sample included only participants who identified as Black or African American and White. This may limit the generalizability of our study’s findings. Future research should prioritize replicating the findings of this study with larger and more racially and ethnically diverse samples to reach data saturation and ensure that FIM program interventions are generalizable and culturally responsive across populations. Furthermore, our study was conducted at a single urban academic medical center CR program, which may also limit the generalizability of our findings for individuals with other chronic conditions and those who may benefit from FIM. Individuals who do not live in urban areas, are enrolled in other rehabilitation programs, or have other chronic conditions not related to cardiac health may offer different perspectives and feedback regarding their unique experiences with healthy eating and the impact of FIM programs. Additionally, the virtual format of our HCD sessions may have impacted the quality of discussion. While conducting the sessions over Zoom ensured that all participants could attend, it may have influenced the way in which participants engaged in discussions. Furthermore, HCD ideally incorporates direct observation of participants engaging with the intervention being developed, a method that was not feasible with the virtual format of our sessions. This may have limited our ability to capture feedback on real-world usability and real-time behavioral and nonverbal responses to our interventions. Future research should incorporate field observation to further refine these interventions. The interventions developed in our study may need to be adapted for use in other settings.

Connecting CR and FIM programs offers a scalable opportunity to improve healthy eating and health outcomes in people with heart conditions. HCD and behavioral science approaches are promising in the development and execution of effective, coordinated nutrition care for these individuals. This research will inform future studies testing the feasibility and efficacy of navigation and/or text messaging to improve participation in FIM among patients with heart disease.